Healthcare-associated infections (HAl) are one of the most serious complications of health care, yet at least one-third of such infections are preventable. The hands of healthcare personnel frequently serve as vectors for the transmission of organisms between patients and are also a major reservoir for pathogens with antimicrobial resistance. Based on recent research regarding hand hygiene, the CDC released a new evidence-based "Hand Hygiene Guideline for Healthcare Settings" in 10/02, which will vastly change current hand hygiene practices. This presents a unique, one-time opportunity to assess the impact this Guideline on nosocomial infection rates, and to strengthen our evidence-based practice regarding prevention and control of infections. The aims of this study are to: (a) assess diffusion and implementation of the new Guideline on hand hygiene practices in acute care; (b) identify barriers to adoption and implementation of the Hand Hygiene Guideline among patient care personnel; (c) compare HAl rates before and after implementation of the Guideline recommendations; and (d) examine the net medical costs and incremental cost-effectiveness of implementation of the Guideline from the hospital perspective. Forty hospitals systematically selected from the National Nosocomial Infection Surveillance System, CDC, will be recruited, allowing detection of 10% or greater differences in HAl rates between those with high and low levels of Guideline implementation. Two-day sites visits will be made to each hospital to determine-by direct observation, written documentation, and interviews--levels of implementation of the Guideline recommendations and barriers to Guideline implementation as perceived by critical care nurses and physicians (n=1,024). Multiple regression modeling will be used to examine the relationships between levels of implementation, perceived barriers to Guideline use, and HAl rates one year before and after Guideline publication within and between hospitals. For the cost analyses, cost data will be obtained directly from the study hospitals as well as from two ongoing R01s in which cost data of hand hygiene and nosocomial infections are being collected (1R01NR/AI05197-01A1, "Staff Hand Hygiene and Nosocomial Infection in Neonates" and AHRQ Grant R01 HS11978, "Outcomes of ICU Working Conditions").